engleski

Measurement of rock resistivity using inductive method in a cased well

Rock conductivity measurement is a pivotal method in the open-hole well logging for evaluation of hydrocarbon reservoirs. The conductivity measurement is also required in cased wells as an addition to the radiation methods. Only a contact conductivity tool is available for the cased well application. This thesis proposes an inductive method for simultaneous measurement of the rock conductivity and the casing properties (thickness, conductivity, and permeability) from within single steel-cased well. The analytical electromagnetic model was derived for a transmitter coil inside a steel casing surrounded by a cylindrically and horizontally layered low-conductive medium. Using the space-frequency analysis of the sensitivity on the casing and formation properties, the measurement configuration consisting of one transmitter and three receiver coils was proposed. The investigation radius, vertical resolution, and separability of the casing and formation contributions were discussed. The inverse problem of determination of the casing and formation properties was based on the Bayesian approach. The method was corroborated on the scaled laboratory model of the cased well. The requirements were established for the electronic instrumentation that would embody the proposed method. The single-well trough-casing inductive tool is found to be feasible for operation in the high-temperature environment using commercially available electronic components. The method is applicable for the rock conductivity larger than 1 S/m with the investigation radius of 10 m.

cased well; rock resistivity; casing inspection; inductive measurement; analytical electromagnetic modelling; inverse problems; Monte Carlo Markov chains; scaled modelling; electronic instrumentation; high temperature environment

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